Electron tube structure and manufacture



Feb. 11, 1958 R. LANDREY ELECTRONYTUBE STRUCTURE AND MANUFACTURE Filed April 20, 1955 2 Sheets-Sheet 1 INVENTOR. LEO R.LANDREY ATTORNEY" Feb. 11, 1958 lfi/R. LANDREY ELECTRON TUBE STRUCTURE AND MANUFACTURE 2 Sheets-Sheet 2 F1166. April 20, 1955 INVENTOR LEO 'R. LANDREY ATTORNEY United States Patent O ELECTRON TUBE STRUCTURE AND MANUFACTURE LeoR. Landrey,Wayne, Pa.,v assignor to Burroughs Corporation, Detroit, Micln, a corporation of Michigan Application April 20, 1955, Serial No. 502,558

18 Claims.. (Cl. 313-157) This invention relates to improvements in electron discharge devices' and more particularly to such devices and the mode of manufacture thereof wherein it is desired toassemble and maintain a plurality of electrodes in a precise relative spatial arrangement.

One type of discharge device which may be constructed in-accordance with this invention'is a magnetron beam switching tube shown and described in an article entitled A new beam switching tube, published in Electronic Design for January 1954. Such a tube also is the subject of .a copending application Serial No. 370,086 entitled lMulti-Position Beam Tube, by S. P. Fan et' al., and which is now United States Patent No. 2,721,955, granted Oct. 25,1955.

A magnetron beam switching tube of this type may have an elongated axial cathode and several circular concentric arrays of other electrodes around it. On the first I or smallest radius from the cathode is an array of spaced spade electrodes. These spade electrodes are of approximately U-shaped cross-section with their convex surfaces facing the cathode.

a beam within the tube and to hold the beam on other electrodes. In line with one side of each spade and on a slightly larger radius is an array of switching electrodes. These switching electrodes are elongated rods and are aligned parallel to the axial cathode. They serve to disturb the stable beam holding function of an associated spade and to cause the beam to switch over to another position in whichit can be stably held. On the next larger radius is an array of beam receiving target electrodes. The target electrodes are arranged in line with the spaces between the spade electrodes so as to receive an electron 'beamdirected thereinto.

Each electron beam position in the type of discharge device referred to hereinabove is formed by an association of one electrode from each of the three different circular arrays. The target electrode of each beam position is disposed between its associated spade and switching electrodes and radially outwardly therefrom to form a pocket into which the .beam is directed when in that position. Preferably, as described in the aforesaid article, the target electrode is provided with an inwardly extending portion which projects toward and may enter the area circumscribed by the spade electrode with which it is associated. The switching electrode is on the other side of the target electrode and adjacent to the spade electrode of the next adjacent beam position. In each beam position, the. spade electrode serves to hold the beam on the target electrode associated therewithwhen the two .are connected to appropriate circuitry and adjusted toappropriate voltages. The switching electrode normally holds the beam from switching from .itsassociated target-electrode to another beam position but when it has its voltage appropriately varied itwill-permit the beam to switch to another position in the=discharge deviceto'strike the next target.

These discharge devices employ an axialmag'neticfield which permeates thearea of the electrodes. Theele'ctron These spades serve to form "netic-electrical-fields ofa magnetron are provided. this device these fields are adjusted to place the tube well Patented Feb. 11,, 1958 beam is urged in'one direction orthe other labout'the cathodedepen'din'g' upon the direction'the magneticflux lines in the tube. This axial magneticfield usually 'may be'provided by a cylindrical permanent magnet but could be provided by an electromagnet or a combination of both type magnets. 'With a positive potential'applied to the spade electrodes and-target electrodes the crossed maginto the magnetron cut-off region, so no beam is formed and no current flows. If the potential of one of the spades is' lowered to nearthe cathode potential, this axially symmetrical field is changed and electrons will flow to the spade having a lowered potential and form a beam which 7 enters the pocket on the side of the spade in the direction the beam is urged by the magnetic field. Some electrons pocket, striking the target electrode thereof. To switch thi's beam to'the next compartment, the switching elec 'trode in the compartment holding thebeam is given a This alters thebeam so that relatively low potential. at least some of it moves toward this switching electrode -and the-spade electrode near it. When some of the beams current flows to this next spade a voltage drop occurs due to this currentflowing through a resistance connecting this second spade to its positive potential. This voltage changecauses the beam to swing on across the spade into the next pocket where the spade acts to hold the beam'in the pocket.

In such devices, electron paths are closely related to the configuration of equipotential lines among the electrodes. These equipotential lines are in turn critically related to the relative spatial arrangement of the electrodes and to their respective potentials. The maintenance of electrode positions within small tolerance-s is essential for reliable performance of such devices. In most devices of thistype, the desired spatial arrangement has been maintained by mounting electrodes on rods or providing tabs on the electrodes and inserting the ends of these tabs and rods in mica 'or ceramic spacers at the upper and lower'ends of the tube. Holes for the desired arrangement were either punched in mica sheets or molded into ceramic discs.

Difliculties have been encountered in the use of such spacers. Mica is prone to flaking and has no more than moderate strength for holding electrodes in position when experiencing accelerations in automatic assembling machinery or in mobile electronic equipment. Also, mica has a smooth surface which must be treated so as to provide a rough surface on which vapors of conductive materials cannot readily condense to form a continuous film which decreases the resistance of various surfaces of the mica. Ceramic end spacers are not subject to this disadvantage, but are much heavier and because of their relatively non-rigid mounting in the tube are likely to cause such tubes to be susceptible to damage when under acceleration.

Also, when ceramic or mica spacers are used, the mounting tabs and rods and the ends of the heater and cathode usually project beyond the spacers into the end zones. If there is any electron emission from heater or cathode in these end zones, highly complex and unwanted discharge paths would be constituted there. Such paths are likely to adversely aflect the main electron discharge characteristics of a tube.

Further, "in such construction, most of the length of each rod and each electrode is unsupported between spacers. Microphonic performance under vibrating 'ac- 3 celeration, and permanent bending or fracture under severe acceleration, may therefore occur.

It is therefore an important object of this invention to produce improved spacing techniques for assembly of electrondischarge devices, to overcome the above mentioned objections.

A more specific object of this invention is to provide a simplified assembly of electrodes and supports for electron discharge devices, removing the need for complex arrangements of mounting rods and spacers.

A further object of this invention is to improve tube reliability by supporting electrodes over their entire length in a precise and constant relative spatial arrangement.

In accordance with one embodiment of the invention low cylindrical body made of insulative material such as ceramic having alternate projections and notches on the *interior side of the cylinder conforming to the electrode configuration of a magnetron beam switching tube and having the different electrodes formed as electrical conductive coatings on the respective surfaces. A single cylindrical body may present certain fabrication difficulties. Accordingly, the cylindrical body may be sub-divided into a plurality of similar triangular or sector shaped ceramic segments. Because of its generally triangular cross section each insulating segment is referred to as a triad. Each triad has different surface portions thereof provided with conductive arrays of coatings firmly secured thereto to serve as electrodes of the magnetron beam switching tube. Further, each triad will provide the surfaces and the conductive coatings for at least one spade, one switching electrode, and one target electrode. As a result of the rigid supporting structure on which these electrodes are mounted, there is no need for the mica end spacers and supporting rods of the conventionally mounted electrodes. When the cylindrical body is subdivided into such segments, the electrodes of more than one compartment or beam receiving position can be provided on each insulative body forming a sub-division of the complete body.

Further, in accordance with this invention, end supports may be provided to maintain the cathode in an axial position and to aid in maintaining the relative positioning of the ceramic segments without depending upon end spacers for maintaining the precise spacing of electrodes on each triad. In one form of the invention the end supports are sealed to the ceramic body to form a vacuum tight enclosure which may serve in lieu of a glass envelope.

In order that this invention may be more clearly understood and more readily carried into effect, it Will be more fully described in connection with the accompanying drawing, in which:

Fig. l is a perspective view, partially broken away, of an electron discharge device utilizing a ceramic structure to position and support electrodes in accordance with the invention;

Fig. 2 is a perspective view of one embodiment of segment or triad useful in constructing an electron discharge device of the character shown in Fig. 1;

Fig. 3 is an elevation of a different embodiment of the invention showing an assembly of triads and end supports and a magnet forming a sealed, relatively shock resistant structure;

Fig. 4 is a sectional view taken along line 44l of Fig. 3; and

Fig. 5 is a side elevation of a further embodiment of the invention.

Referring now to the drawing, Fig. 1 shows a magnetron beam switching tube constructed in accordance with this invention. A magnet 12 surrounds tube 10, producing an axial magnetic field. Electrode supporting elements or triads 13 of insulating material, one of which is shown in enlarged scale in Fig. 2, are generally sector shaped so that they form a body of cylindrical configuration when placed in a successively abutting relationship. The axis of this cylindrical body coincides with that of cathode 14 and the cathode determines the axis of the tube. The portions of the insulative body approaching nearest to this cathode form convex surfaces upon which the spade electrodes 19 are coated. Each triad 13 of this body is notched on one side and coated with conductive material on two surfaces of the notch to provide the L-shaped target electrode 21. On the other side of the spade portion of the triad a narrow conductive strip is applied and provides the switching electrode 20. Spacer elements 1515 at the opposite ends of the triad assembly assist in maintaining the arrangement of triads 13 in their inter-locked position within an evacuated glass envelope 16. Base supports connecting pins 18 which are electrically connected to the different electrodes formed upon the triad 13. Reference will be made hereinafter to a form of interconnection between the tube electrodes and the pins 8.

Each segment or triad is formed of insulating material such as a ceramic substance. It is provided with a radial portion which projects toward the axis of the tube and a lateral portion which projects in one direction from the outer end of the radial portion. When a plurality of similar triads are assembled they assume the hollow cylindrical or sleeve form illustrated in Figs. 1 and 4. The

Depending on the direction of the lines of flux from the magnetic source, the electron beam will be urged to rotate in a clockwise or counter-clockwise direction around the cathode. In this instance the parts of the device are arranged to rotate the beam in a clockwise direction as viewed in Fig. 4. The direction of beam advancement (clockwise) is opposite to the direction of electron paths around the cathode. When a switching grid is lowered in potential while the beam is held in its compartment,

the beam fans out, mostly in the direction from which the electrons are coming, or upstream in the beam. This causes the beam to advance in this upstream direction rather than in the same direction as electron flow.

As shown in detail in Fig. 2, each segment or triad 13 is provided with a plurality of electrodes which are formed as coatings or surfaces of electrically conductive material. Spade electrode 19 is the innermost coated electrode, on the convex or U-shaped surface of triad 13. A coated switching grid 20 is adjacent to spade electrode 19 on one side, and the coated L-shaped target electrode 21 is affixed to surface portions of the recess on the other side of triad 13. Should additional electrodes be required, such as electrode 22, they also may be affixed to the triad. Additional shapes or forms of electrode receiving structures could be made in a similar manner, if desired.

To provide the interconnection between the electrode coatings and the pins 18, the lower end of each triad is provided with. coated extension strips 23 which connect each to a different coated electrode on the triad. Holes 24 are provided in the lower end of each triad 13 for insertion ofconnecting pins 25. These holes may be arranged to pass through the conducting strips 23 as shown. Pins 25 are used for axial or end connections to the electrodes as well as to assist in placing the end supports on an assembly of triads 13. When radial leads are required, strips 23 may be extended to form leads 23a.

Each segment or triad 13 may have side surfaces 26 and 27 radially related to are surface 28 to form a sector of such central angle that a plurality of similar abutting triads form a cylindrical array; Thus, a plurality of identical triads may be placed in successively abutting relationship with surface 26 of one segment against surface 27 of another, and so on, until an arrangement is constructed as shown in Fig. 4. It will be evident that in this instance each segment must be an integer-denominator fraction /2, /3, A, A etc., of a whole cylinder, for the assembly to form a cylinder.

When a plurality of segments are placed in a successively abutting arrangement and end supports are placed on them as shown in Fig. 3, then connecting pins can be inserted into mating apertures of both end supports 15-15 and triads 13, making contact with the strips 23. Where leads are required, long pins 2511 are used, and for supporting purposes only short pins 25b are used. Cathode 14 also is mounted in end supports 15 for centered position in tube 10.

Fig. 4 shows the electrode system which is constructed when ten sectorial segments 13 of 36 each are held in an abutting arrangement. Surfaces 26 and 27 of triad 13 may be coated with bonding material which holds these abutting surfaces firmly together after assembly and processing, such as heating. Also, the end spacers 15 may be bonded tothe triads. Thus, the assembly of triads 13 and end supports 15 may be used to form the gas tight envelope of a vacuum tube. In this case bonding material is placed along the outer edge 29a of the end triad surface 29 and on a narrow outer ring of end supporter surface 15a of end supports 15. These edge areas are marked off by dotted lines in Fig. 2. Pins 25 and cathode 14 also are. bonded to end supports 15 when the gas-tight assembly is produced. To provide for evacuation of this assembly, it canbe placed in a vacuum chamber and evacuated prior to heating to bond the segments and end pieces .together, or an evacuating stem 31 may be provided as shown in Fig. 3.

A magnet is required to provide the axial magnetic field essential for magnetron type operation. In the embodiment of the invention illustrated in Figs. 3 and 4, a magnet 12' is mounted directly on the ceramic body. After the assembly of triads 13 and plates 15 are bonded into amonolithic body, magnet 12' is slid over the assembly to the position shown in Figs. 3 and 4. Though shown in sectional and broken views, magnet 12' is a full cylinder. Since the ceramic triads and end plates join to form a precisely dimensioned body, the clearances between the cylindrical magnets inner diameter and the triad assemblys outer diameter can be held to very close tolerances. As a result, there is a friction-fit between them. It is. within the scope ofthe invention to provide even closer tolerances by a grinding process which grinds the outer diameter of this ceramic body precisely to a desired dimension. As magnet 12' is slid onto the ceramic bodyof the tube, bonding material may be applied to the surfaces of the magnet and tube body which will contact so that magnet 12' is firmly bonded to the assembly'of triads and end spacers onceit is driven onto them. It forms therewith a shock resistant vacuum tube structure.

Other means for holding triads in position can be used. Thus, in Fig. 5, pressure from an encircling garter type spring 30, or from several such springs, holds the triads in abutting relationship. Connecting pins 25a hold end supports 15 also in thi s'embodiment, and provide electrical connections at either or both ends as required. Without bonding on the abutting surfaces, an outer gas-tight envelope 16 is required, as in Fig. 1.

With the structure of triads 13, it will be seen that electrodes 19--22 are held in a precise spatial relationship withouta complex assembly of tabs, rods, and spacers. Further, each electrode is supported throughout-its entire length and area by the insulating segments of substantial cross-section thereby preventing deformed spacing by bending or vibration.

relative positions of the electrodes. For example, an, exu truded ceramic form of the general shape shown in Fig.

. 2 may be used, and conductive electrode surfaces may be plated or sprayed on the entire triad surface with the exception of the arc surface 28. Then, by controlled grinding or etching techniques the conductive surface may be removed from unwanted places such as the surfaces 26 and 27. For example, a thin grinding instrument may machine out the groove 38 to separate electrode surfaces 19 and 21. It is clear therefore that the electrode structure may be readily manufactured to form precise electrode spacing not subject to deformation in subsequent assembly steps.

Therefore, from the above description of the tube electrode structure and mode of tube assembly, it isseen that precise control of electrode spacing may be accomplished inexpensively in a readily assembled tube structure in accordance with the teachings of this invention.

What is claimed is:

1. In an electron discharge device an insulative memher, a U-shaped electrode formed on a convex surface of said insulative member by conductive coating thereon, an L shaped electrode formed on an angular surface of said insulative member by conductive coating thereon, and a narrow strip electrode formed on said insulative member by conductive coating thereon.

2. In an electron discharge device, a plurality of ceramic segments, a plurality of elongated electrodes coated on each of said segments to fully support their respective areas, and means to hold said segments in a cylindrical array within the electron discharge device.

3. An electron discharge device comprising a cathode, a ceramic body surrounding said cathode, a plurality of electrodes supported throughout their area on said ceramic body and symmetrically arranged around said cathode, and a magnetic structure surrounding said' ceramic body.

4. A device as defined in claim 3 wherein the ceramic body comprises a plurality of discrete elements, and means provided bonding the elements. together in an air tight envelope. I

5. In an electron discharge device, a plurality of, insulator segments, a plurality of electrodes on each of said segments, and means for retaining said segments. in successively abutting arrangement to hold said. electrodes in a precise relative spatial arrangement.

6. In an electron discharge device, a plurality of identical ceramic segments, and a plurality of metallic coatings on each of said ceramic segments to provide electrodes on said segments, and means to hold said segments and electrodes in a precise spatial relationship to one another.

7. In an electron discharge device, a plurality of identical sector shaped ceramic segments, a plurality of electrodes on each of said ceramic segments, and means for holding said segments in a circular abutting relationship to hold said electrodes in a precise spatial relationship about a common axis.

8. An electron discharge device comprising a plurality of identical ceramic sectors, a plurality of metallic coatings, on each of. said ceramic sectors, a pair of end supports, connectors mounted in said end supports, a cathode and means for holding said segments in successively abutting arrangement and said cathode equidistant from said sectors whereby said cathode and said electrodes are held in precise spatial relationship.

9. In an electrical discharge device, a plurality of identical ceramic segments of sector-shaped crosssection, more than two metallic coatings on each of said ceramic segments, end supports, means for holding said ceramic segments in a circular successively abutting relationship,

' 7 and connectors for contacting said metallic coatings and holding said end supports and said segments in a unified g structure.

10. In an electrical discharge device a ring of identical ceramic sectors, a U-shaped electrode coated on a convex surface of each of said ceramic sectors, an L'shaped electrode coated on a notched surface of each of said ceramic sectors on one side from said convex surface, and a narrow strip electrode coated on another surface of each of said ceramic sectors, means for holding said segments in a precise spatial arrangement presenting a cylindrical outer surface, and magnetizing means including a cylindrical magnetic structure closely fitting said cylindrical assembly of ceramic sectors.

11. In an electrical discharge device, a ring of successively abutting ceramic segments, and a plurality of metallic coatings on surfaces of each of said ceramic segments, whereby said metallic coatings are held in a precise spatial relationship.

12. An electron discharge device comprising a cathode, a ceramic body surrounding said cathode, a plurality of U-shaped electrodes in a circular 'array around said cathode and supported throughout their area on said ceramic body, a plurality of L shaped electrodes in a larger-radius circular array than the array of said plurality of U-shaped electrodes and supported throughout their area on said ceramic body, a plurality of switching electrodes arranged in a circular array of radius intermediate the radii of the array of U-shaped electrodes and the array of L shaped electrodes and supported throughout their area on said ceramic body, and magnetizing means providing an axial magnetic field through said electron discharge device, said magnetizing means including a cylindrical magnetic structure closely fitting the outer diameter of said ceramic body.

13. In an electron discharge device a plurality of ceramic segments, an elongated U-shaped electrode coated on a convex surface of each of said segments, an L- shaped electrode coated on a notched surface of each of said segments, a narrow strip electrode coated on another surface of each of said segments, means to hold said segments in a cylindrical array within the electron discharge device, and magnetic means surrounding and firmly bonded to said cylindrical array of ceramic segments to provide an axial magnetic field through said electron discharge device.

14. An electron discharge device comprising a cathode, a ceramic body surrounding said cathode, a plurality of convex electrodes formed on convex inner surfaces of said ceramic body, a plurality of L-shaped electrodes formed on angular inner surfaces of said ceramic body, a plurality of rod-shaped electrodes formed on surfaces of said ceramic body intermediate between said convex surfaces and said angular surfaces, and a magnetic structure closely surrounding said ceramic body.

15. In a magnetron type electron beam switching device having crossed electrostatic and magnetic fields, a cathode elongated in the direction of the flux lines of the magnetic field, a hollow cylindrical shaped body concentrically encircling the cathode and formed of rigid electrical insulative material, the interior of the body being shaped to provide an alternate series of inwardly projecting ridges and inwardly opening cavities, metallic coatings on the projecting ridges of the body and constituting the spade electrodes of the device for directing and holding an electron beam emitted from the cathode in a selected one of said cavities, metallic coatings on the bases of the cavities of the body and constituting the target electrodes of the device upon which the electron beam impinges, and metallic coatings on similar sides of the cavities of the body and constituting the switching electrodes of the device for shifting the electron beam out of the cavity in which it is directed into another cavity of the body, the coatings having surface areas of the insulative body therebetween and being precisely supported by and insulated from one another by the rigid supporting character of the body.

16. In a magnetron type electron beam switching device having crossed electrostatic and magnetic fields, a cathode elongated in the direction of the flux lines of the magnetic field, a hollow cylindrical shaped body concentrically encircling the cathode and formed of rigid electrical insulative material, the interior of the body being shaped to provide an alternate series of inwardly projecting ridges and inwardly opening cavities, metallic coatings on the projecting ridges of the body and constituting the spade electrodes of the device for directing and holding an electron beam emitted from the cathode in a selected one of said cavities, and metallic coatings on the bases of the cavities of the body and constituting the target electrodes of the device upon which the electron beam impinges, the coatings having surface areas of the insulative body therebetween and being precisely sup ported by and insulated from one another by the rigid supporting character of the body.

17. A magnetron type electron discharge device comprising, in combination, an elongated cathode, a hollow cylindrically shaped body concentrically encircling the cathode and formed of rigid electrical insulative material, the interior of the body being shaped to provide an alternate series of inwardly projecting ridges and inwardly opening cavities, metallic coatings on the projecting ridges of the body and constituting the spade electrodes of the device for directing and holding an electron beam emitted from the cathode in a selected one of said cavities, metallic coatings on the bases of the cavities of the body and constituting the target electrodes of the device upon which the electron beam impinges, metallic coatings on similar sides of the cavities of the body and constituting the switching electrodes of the device for shifting the electron beam out of the cavity in which it is directed into another cavity of the body, the coatings having surface areas of the insulative body therebetween and being precisely supported by and insulated from one another by the rigid supporting character of the body, and a sleeve shaped magnetic structure encircling said body and providing a magnetic field in the interior of the body having the direction of its flux lines extending substantially parallel to the cathode.

18. An electron discharge device comprising, in combination an elongated cathode, a rigid body of electrically insulative material concentrically surrounding said cathode in radial spaced relation thereto, a plurality of spade electrodes formed on convex inner surfaces of said ceramic body, a plurality of target electrodes formed on recessed surfaces of said body between said spade electrodes, a plurality of switching electrodes formed on surfaces of said body intermediate said spade electrodes and said target electrodes, a magnetic structure surrounding said body and providing magnetic flux lines in the interior thereof extending substantially parallel to the cathode, separate electrically conductive pathways formed on one end of the body and individually connected to said spade, target and switching electrodes, and electrically conductive pins projecting from said end of the body and each having one end thereof aflixed to a slected one of the conductive pathways.

References Cited in the file of this patent UNITED STATES PATENTS 2,084,867 Prinz et al. June 22, 1937 2,629,068 Gottschalk et al Feb. 17, 1953 2,684,452 Sorg July 20, 1954 

